Electrical Activity of Crystal Defects in Multicrystalline Si

Upgraded metallurgical-grade silicon solar cells with different ranges of efficiencies have been characterized by light-beam-induced current (LBIC) measurements. The interaction between grain boundaries and metallic impurities is studied for cells fabricated on wafers from different solidification heights of the ingot. A tight relation is observed between the electrical activity of the grain boundaries and the position of the wafer in the ingot, which is related to the impurity contamination. The presence of a large amount of metallic impurities enhances the electrical activity of the grain boundaries. The main features of the LBIC images are discussed in relation to the presence of metallic impurities.